In the past, bulky, cumbersome hooks and couplings have been used to suspend cargo from helicopters, derricks, cranes. Besides, detaching cargo from hoist cables has required personnel to be present at the loading platform area. Perhaps this is one reason why single point operation has been preferred over multi-point operation, particularly for externally--slung helicopter loads. Time is consumed in detaching cargo from the hoist and the more hooks to disengage, the more time required to remove the cargo. If the load's removal can be done automatically upon its contact with the platform and with a minimum of time and effort, then two-point operation would be preferred. With two-point suspension, there would be less swaying and twisting of the load, particularly under wind--gusty conditions. The helicopter pilot would be able to control his aircraft better, as a swaying load would increase the pilot's workload, if not make impossible a precise unloading operation.
Suspended cargo from helicopters would become more popular, using the devices described here. Also, the need for skilled personnel at the loading area to remove cargo would be unnecessary. Just any laborer could remove cargo, should ground personnel be required. For example, there are no signal wires to detach in most of the techniques described.
The Boeing heavy lift helicopter (Vol.II S 301-10000-2 of 31 Oct. 1973, contract DAA J01-71-C-0840(P40)), states that hook-up time to a prepared load is to be performed in no more than two (2) minutes. A cable, separate from the hoist tension member and attached directly to each coupling, deployed from a separately powered cable reel, mounted adjacent to the main hoists, is recommended by Boeing helicopters. The cable carries conductors for mechanizing a remote mechanical hook release system, and runs from the coupling at the load to the crew station within the aircraft. Using the release mechanism suggested here, one could omit the above remote electrically--actuated hook release system. An electrically actuated hook wound complicate the release system, and sending electrical signals through long conductors to release hooks may not be an altogether reliable operation.
Besides, Boeing recommends a cable assembly with a protective outer braid metal sheath, for protecting and supporting the conductors and providing a tension load path so as to be used as a back-up for a mechanical--pull coupling--release. Such a cable would add substantial weight to the aircraft, while a lightweight cord to remove a magnet, as described here, would contribute very little weight. Since no electrical signals are required for remotely releasing a load, there would be no problems associated with the possibility of the signal path becoming open-circuited, in the techniques described here.
The need, particularly by the U.S. Navy, for a quick load release system is apparent when one realizes that the military must load and unload ships quickly, if it is going to win battles and save personnel and equipment under adverse conditions.
In offshore ship-loading,, the problem of suspended, swinging containerized loads exists under wind gust conditions, making the loading operation hazardous to ship personnel. A previous U.S. Pat. No. 4,054,103, shows how this problem can be reduced by means of inflated paddings.
In one or more of the techniques described here, ship personnel at the loading area may be eliminated, thus reducing the hazardous conditions described in U.S. Navy reports, such as AD-A030 365/1st August 1976, by L. Bonde and David Dillon.
To satisfy the military, the last two techniques described include solenoids and a wedge-shaped member, which assure that the scissorlike part maintain engagement with a doughnut-shaped part until the solenoids are actuated remotely. With the wedge-shaped part removed, the scissorlike part collapses, allowing it to slip through the central hole of the doughnut-shaped part.